/*
 * Copyright 2012-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cn.springcloud.gray.bean.properties.bind;

import java.beans.PropertyEditor;
import java.lang.annotation.Annotation;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.Consumer;

import org.springframework.beans.BeanUtils;
import org.springframework.beans.PropertyEditorRegistry;
import org.springframework.beans.SimpleTypeConverter;
import org.springframework.beans.propertyeditors.FileEditor;
import cn.springcloud.gray.bean.convert.ApplicationConversionService;
import org.springframework.core.ResolvableType;
import org.springframework.core.convert.ConversionException;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.converter.ConditionalGenericConverter;
import org.springframework.core.convert.support.GenericConversionService;
import org.springframework.util.Assert;

/**
 * Utility to handle any conversion needed during binding. This class is not thread-safe
 * and so a new instance is created for each top-level bind.
 *
 * @author Phillip Webb
 * @author Andy Wilkinson
 */
final class BindConverter {

    private static final Set<Class<?>> EXCLUDED_EDITORS;

    static {
        Set<Class<?>> excluded = new HashSet<>();
        excluded.add(FileEditor.class); // gh-12163
        EXCLUDED_EDITORS = Collections.unmodifiableSet(excluded);
    }

    private static BindConverter sharedInstance;

    private final ConversionService conversionService;

    private BindConverter(ConversionService conversionService,
                          Consumer<PropertyEditorRegistry> propertyEditorInitializer) {
        Assert.notNull(conversionService, "ConversionService must not be null");
        List<ConversionService> conversionServices = getConversionServices(
                conversionService, propertyEditorInitializer);
        this.conversionService = new CompositeConversionService(conversionServices);
    }

    private List<ConversionService> getConversionServices(
            ConversionService conversionService,
            Consumer<PropertyEditorRegistry> propertyEditorInitializer) {
        List<ConversionService> services = new ArrayList<>();
        services.add(new TypeConverterConversionService(propertyEditorInitializer));
        services.add(conversionService);
        if (!(conversionService instanceof ApplicationConversionService)) {
            services.add(ApplicationConversionService.getSharedInstance());
        }
        return services;
    }

    public boolean canConvert(Object value, ResolvableType type,
                              Annotation... annotations) {
        return this.conversionService.canConvert(TypeDescriptor.forObject(value),
                new ResolvableTypeDescriptor(type, annotations));
    }

    public <T> T convert(Object result, Bindable<T> target) {
        return convert(result, target.getType(), target.getAnnotations());
    }

    @SuppressWarnings("unchecked")
    public <T> T convert(Object value, ResolvableType type, Annotation... annotations) {
        if (value == null) {
            return null;
        }
        return (T) this.conversionService.convert(value, TypeDescriptor.forObject(value),
                new ResolvableTypeDescriptor(type, annotations));
    }

    static BindConverter get(ConversionService conversionService,
                             Consumer<PropertyEditorRegistry> propertyEditorInitializer) {
        if (conversionService == ApplicationConversionService.getSharedInstance()
                && propertyEditorInitializer == null) {
            if (sharedInstance == null) {
                sharedInstance = new BindConverter(conversionService,
                        propertyEditorInitializer);
            }
            return sharedInstance;
        }
        return new BindConverter(conversionService, propertyEditorInitializer);
    }

    /**
     * A {@link TypeDescriptor} backed by a {@link ResolvableType}.
     */
    private static class ResolvableTypeDescriptor extends TypeDescriptor {

        ResolvableTypeDescriptor(ResolvableType resolvableType,
                                 Annotation[] annotations) {
            super(resolvableType, null, annotations);
        }

    }

    /**
     * Composite {@link ConversionService} used to call multiple services.
     */
    static class CompositeConversionService implements ConversionService {

        private final List<ConversionService> delegates;

        CompositeConversionService(List<ConversionService> delegates) {
            this.delegates = delegates;
        }

        @Override
        public boolean canConvert(Class<?> sourceType, Class<?> targetType) {
            Assert.notNull(targetType, "Target type to convert to cannot be null");
            return canConvert(
                    (sourceType != null) ? TypeDescriptor.valueOf(sourceType) : null,
                    TypeDescriptor.valueOf(targetType));
        }

        @Override
        public boolean canConvert(TypeDescriptor sourceType, TypeDescriptor targetType) {
            for (ConversionService service : this.delegates) {
                if (service.canConvert(sourceType, targetType)) {
                    return true;
                }
            }
            return false;
        }

        @Override
        @SuppressWarnings("unchecked")
        public <T> T convert(Object source, Class<T> targetType) {
            Assert.notNull(targetType, "Target type to convert to cannot be null");
            return (T) convert(source, TypeDescriptor.forObject(source),
                    TypeDescriptor.valueOf(targetType));
        }

        @Override
        public Object convert(Object source, TypeDescriptor sourceType,
                              TypeDescriptor targetType) {
            for (int i = 0; i < this.delegates.size() - 1; i++) {
                try {
                    ConversionService delegate = this.delegates.get(i);
                    if (delegate.canConvert(sourceType, targetType)) {
                        return delegate.convert(source, sourceType, targetType);
                    }
                } catch (ConversionException ex) {
                }
            }
            return this.delegates.get(this.delegates.size() - 1).convert(source,
                    sourceType, targetType);
        }

    }

    /**
     * A {@link ConversionService} implementation that delegates to a
     * {@link SimpleTypeConverter}. Allows {@link PropertyEditor} based conversion for
     * simple types, arrays and collections.
     */
    private static class TypeConverterConversionService extends GenericConversionService {

        TypeConverterConversionService(Consumer<PropertyEditorRegistry> initializer) {
            addConverter(new TypeConverterConverter(createTypeConverter(initializer)));
            ApplicationConversionService.addDelimitedStringConverters(this);
        }

        private SimpleTypeConverter createTypeConverter(
                Consumer<PropertyEditorRegistry> initializer) {
            SimpleTypeConverter typeConverter = new SimpleTypeConverter();
            if (initializer != null) {
                initializer.accept(typeConverter);
            }
            return typeConverter;
        }

        @Override
        public boolean canConvert(TypeDescriptor sourceType, TypeDescriptor targetType) {
            // Prefer conversion service to handle things like String to char[].
            if (targetType.isArray()
                    && targetType.getElementTypeDescriptor().isPrimitive()) {
                return false;
            }
            return super.canConvert(sourceType, targetType);
        }

    }

    /**
     * {@link ConditionalGenericConverter} that delegates to {@link SimpleTypeConverter}.
     */
    private static class TypeConverterConverter implements ConditionalGenericConverter {

        private final SimpleTypeConverter typeConverter;

        TypeConverterConverter(SimpleTypeConverter typeConverter) {
            this.typeConverter = typeConverter;
        }

        @Override
        public Set<ConvertiblePair> getConvertibleTypes() {
            return Collections.singleton(new ConvertiblePair(String.class, Object.class));
        }

        @Override
        public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
            return getPropertyEditor(targetType.getType()) != null;
        }

        @Override
        public Object convert(Object source, TypeDescriptor sourceType,
                              TypeDescriptor targetType) {
            SimpleTypeConverter typeConverter = this.typeConverter;
            return typeConverter.convertIfNecessary(source, targetType.getType());
        }

        private PropertyEditor getPropertyEditor(Class<?> type) {
            SimpleTypeConverter typeConverter = this.typeConverter;
            if (type == null || type == Object.class
                    || Collection.class.isAssignableFrom(type)
                    || Map.class.isAssignableFrom(type)) {
                return null;
            }
            PropertyEditor editor = typeConverter.getDefaultEditor(type);
            if (editor == null) {
                editor = typeConverter.findCustomEditor(type, null);
            }
            if (editor == null && String.class != type) {
                editor = BeanUtils.findEditorByConvention(type);
            }
            if (editor == null || EXCLUDED_EDITORS.contains(editor.getClass())) {
                return null;
            }
            return editor;
        }

    }

}
